The use of quantitative cultures and antibody coating of bacteria to diagnose bacterial pneumonia by fiberoptic bronchoscopy

The value of antibody-coated bacteria in tracheal aspirates for the diagnosis of ventilator-associated pneumonia: a case-control study

Objective:

Ventilator-associated pneumonia (VAP) is the leading type of hospital-acquired infection in ICU patients. The diagnosis of VAP is challenging, mostly due to limitations of the diagnostic methods available. The aim of this study was to determine whether antibody-coated bacteria (ACB) evaluation can improve the specificity of endotracheal aspirate (EA) culture in VAP diagnosis.

Methods:

We conducted a diagnostic case-control study, enrolling 45 patients undergoing mechanical ventilation. Samples of EA were obtained from patients with and without VAP (cases and controls, respectively), and we assessed the number of bacteria coated with FITC-conjugated monoclonal antibodies (IgA, IgM, or IgG) or an FITC-conjugated polyvalent antibody. Using immunofluorescence microscopy, we determined the proportion of ACB among a fixed number of 80 bacteria.

Results:

The median proportions of ACB were significantly higher among the cases (n = 22) than among the controls (n = 23)-IgA (60.6% vs. 22.5%), IgM (42.5% vs. 12.5%), IgG (50.6% vs. 17.5%), and polyvalent (75.6% vs. 33.8%)-p < 0.001 for all. The accuracy of the best cut-off points for VAP diagnosis regarding monoclonal and polyvalent ACBs was greater than 95.0% and 93.3%, respectively.

Conclusions:

The numbers of ACB in EA samples were higher among cases than among controls. Our findings indicate that evaluating ACB in EA is a promising tool to improve the specificity of VAP diagnosis. The technique could be cost-effective and therefore useful in low-resource settings, with the advantages of minimizing false-positive results and avoiding overtreatment.

Clinical Aspects of Upper and Lower Respiratory Tract Infections

Respiratory tract infections are among the most common illnesses leading to medical consultation, and are associated with significant mortality. Community-acquired pneumonia is a common illness and, while Streptococcus pneumoniae continues to be the most frequent causative agent, atypical pathogens such as Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella species are now identified as additional common aetiological agents. Since clinical and roentgenographic features poorly predict the aetiological agent in most cases of community-acquired pneumonia, empirical therapy is generally recommended. Nosocomial pneumonia is the second most common hospital-acquired infection and is associated with significant mortality. Aerobic Gram-negative bacilli and Staphylococcus aureus are the predominant causative pathogens. New techniques to improve the diagnosis of nosocomial pneumonia have been introduced, but their role has not been entirely clarified. Therapy directed toward the most likely pathogens (aerobic Gram-negative species and S. aureus) on an empirical basis is recommended until more specific information is obtained. Acute exacerbations of chronic bronchitis should be treated with antimicrobial therapy directed toward S. pneumoniae, Haemophilus influenzae or Moraxella catarrhalis. Because of the emergence of β-lactamase-producing strains of H. influenzae and M. catarrhalis, the choice of an antimicrobial agent has to be carefully considered. Group A β-haemolytic streptococci are the most common cause of bacterial pharyngitis and penicillin remains the drug of choice. Patients suffering from otitis media and sinusitis are infected with the same organisms as those patients with acute exacerbations of chronic bronchitis and antibacterial choices are therefore similar.

Diagnostic testing for community-acquired pneumonia

The microbial cause of community-acquired pneumonia can be identified by noninvasive means in the majority of cases, usually within a few days of presentation. The Gram stain and culture of a pretreatment sputum sample are the most useful tests, but have significant limitations. Methods for detecting pneumococcal antigen in respiratory secretions are particularly helpful in patients who have received antibiotics before evaluation. Testing for specific pathogens such as L. pneumophila, M. pneumoniae, or C. pneumoniae should be guided by clinical suspicion in individual circumstances. Invasive procedures are most helpful in patients suspected of having infection with opportunistic or resistant pathogens, and in those whose initial management has been unsuccessful.

The diagnosis of ventilator-associated pneumonia: a comparison of histologic, microbiologic, and clinical criteria

STUDY OBJECTIVE

To evaluate histologic, microbiological, and clinical criteria in the recognition of ventilator-associated pneumonia (VAP) in patients who died while mechanically ventilated.

METHODS

The study group consisted of 39 patients who died after a mean of 14 days of mechanical ventilation. Postmortem fiberoptic bronchoscopy (FOB) and open lung biopsy were performed with collection of specimens initiated <1 h after death. The microbiological specimens included suction catheter aspirate of tracheal secretions, FOB-guided protected specimen brush (PSB) of tracheal secretions, blindly placed PSB in a distal airway, FOB-guided PSB in a distal airway, and FOB-guided BAL fluid (BALF) in a distal airway. Qualitative bacteriologic study was performed on all specimens, and quantitative bacteriologic study was performed on all but the suction catheter aspirate of the trachea. A biopsy specimen of peripheral lung parenchyma from the same region sampled by FOB was sent for quantitative culture and histologic analysis. The BALF was analyzed for cell population and percent of neutrophils containing intracellular organisms. The clinical criteria selected for comparison with histologic and microbiological results included a temperature > or =38.5 degrees C during the 48 h prior to death, a WBC count > or =15,000/mm3 in the 48 h prior to death, presence of a bacterial or fungal pathogen on the last sputum culture, radiographic worsening in the week prior to death, and worsening gas exchange defined as a 15% decrease in the PaO2/fraction of inspired oxygen ratio in the 72 h prior to death.

RESULTS

None of the quantitative cultures had a reliable positive predictive value for histologic pneumonia. None of the five clinical criteria tested showed agreement with the presence or absence of histologic pneumonia. There was a significant correlation between qualitative and quantitative microbiological results from the distal airway/FOB-guided PSB, distal airway/BALF, and quantitative culture of the lung parenchyma. Also, suction catheter aspirate of the trachea had a sensitivity of 87% in recognizing the bacterial species simultaneously present in lung parenchyma. None of the patients with histologic pneumonia had <50% neutrophils in the BALF.

CONCLUSIONS

Neither the bacterial, density from the four airway quantitative cultures, nor the bacterial density from quantitative culture of lung parenchyma accurately separated the histologic pneumonia and nonpneumonia groups. No clinical criteria or combination of clinical criteria correlated with the presence or absence of histologic pneumonia. A BALF with <50% neutrophils had a 100% negative predictive value for histologic pneumonia. A BALF quantitative culture had a sensitivity of 63%, specificity of 96%, and positive predictive value of 91% in recognizing sterile lung parenchyma. Thus, BALF may have a role in excluding pneumonia/infection in the ventilated patient. Antibiotic choice for the empiric therapy of VAP can be accurately guided by the microbial population recognized through culture of a tracheal suction catheter aspirate.

Bronchoscopic diagnosis of pneumonia

Lower respiratory tract infections are characterized by significant morbidity and mortality but also by a relative inability to establish a specific etiologic agent on clinical grounds alone. With the recognized shortcomings of expectorated or aspirated secretions toward establishing an etiologic diagnosis, clinicians have increasingly used bronchoscopy to obtain diagnostic samples. A variety of specimen types may be obtained, including bronchial washes or brushes, protected specimen brushings, bronchoalveolar lavage, and transbronchial biopsies. Bronchoscopy has been applied in three primary clinical settings, including the immunocompromised host, especially human immunodeficiency virus-infected and organ transplant patients; ventilator-associated pneumonia; and severe, nonresolving community- or hospital-acquired pneumonia in nonventilated patients. In each clinical setting, and for each specimen type, specific laboratory protocols are required to provide maximal information. These protocols should provide for the use of a variety of rapid microscopic and quantitative culture techniques and the use of a variety of specific stains and selective culture to detect unusual organism groups.

New approaches in the diagnosis of nosocomial pneumonia

We have presented a review of the present literature on new modalities to diagnose nosocomial pneumonia. Procedures are now available that, when correctly used, can establish a diagnosis of pneumonia with a high degree of reliability. In our institution, reliance on bronchoscopic modalities has simplified management of patients with suspected VAP, by eliminating confusion and rationalizing antibiotic treatment. Invasive procedures, however, should be performed only if the results of cultures are consistently applied to treatment. As this field rapidly evolves, we hope that this review will provide the reader with a foundation to understand new developments.

Pneumococcal antigen detection in bronchoalveolar lavage fluid from patients with pneumonia

BACKGROUND

Pneumococcal pneumonia can be diagnosed by the detection of capsular antigen in sputum, serum, pleural fluid, or urine using countercurrent immunoelectrophoresis and latex agglutination. In addition, quantitative cultures of bronchoalveolar lavage (BAL) fluid are also reliable for establishing the aetiology of pneumonia. This study investigated the value of rapid detection of pneumococcal antigen in BAL fluid from patients with pneumonia.

METHODS

Pneumococcal antigen was detected by countercurrent immunoelectrophoresis and latex agglutination. Patients were grouped according to BAL quantitative culture results into pneumococcal pneumonia (n = 24), other known aetiology (n = 18), and unknown aetiology (n = 17). Thirteen patients with interstitial lung disease and without pneumonia served as a control group.

RESULTS

In patients with pneumococcal pneumonia, antigen was detected by countercurrent immunoelectrophoresis in 50% and by latex agglutination in 54% of cases. In patients with pneumonia of unknown aetiology pneumococcal antigen was detected by latex agglutination in 53% of cases. Antigen was not detected in patients with pneumonia of other known aetiology or in control patients, yielding a specificity of 100%.

CONCLUSIONS

In patients with pneumococcal pneumonia requiring fibreoptic bronchoscopy detection of pneumococcal antigen in BAL fluid may rapidly and accurately confirm the aetiology. Furthermore, in nearly half the cases of pneumonia of unknown aetiology antigen can be detected, suggesting that Streptococcus pneumoniae is a major causative agent in such patients.

A clinical profile of chronic bacterial pneumonia. Report of 115 cases

OBJECTIVE

To review the clinical presentation, radiology, microbiology, and response to therapy of patients with chronic bacterial pneumonia.

DESIGN

A retrospective analysis.

SETTING

An urban tertiary care medical center.

PARTICIPANTS

One hundred fifteen patients with pulmonary and/or constitutional symptoms of at least 1 month's duration with 4,000 or more colony-forming units (CFUs) of a single bacterial species identified by quantitative culture obtained via fiberoptic bronchoscopy.

MEASUREMENTS

Charts were analyzed for presence or absence of any predisposing illness, symptoms at presentation, roentgenographic abnormalities, microbiologic results, findings at fiberoptic bronchoscopy, and results of therapeutic intervention.

RESULTS

Sixty-five percent of patients with chronic bacterial pneumonia had a predisposing disease, 35 percent were "normal." Cough, fatigue, dyspnea, and weight loss were predominant symptoms in both groups. Bronchogenic carcinoma was newly diagnosed in 16 patients (14 percent). Haemophilus influenzae or alpha-hemolytic streptococcus was isolated in 68 percent of patients. Risk of recurrence of infection was inversely associated with duration of therapy in both groups.

CONCLUSIONS

Chronic bacterial pneumonia is more common than previously recognized. It occurs in patients with and without a predisposing illness. Clinical presentation, roentgenographic appearance, and bacteriology are similar between the two groups. Cure requires prolonged antibiotic therapy.

Detection of antibody-coated bacteria in expectorated sputum for diagnosis of lower respiratory infections

We evaluated antibody-coated bacteria (ACB) in expectorated sputum to discriminate contaminating or colonizing organisms from true pathogens. We examined 60 expectorated sputum samples from 51 patients with lower respiratory infections (chronic obstructive pulmonary disease 25, pneumonia 20, purulent tracheobronchitis 6). All samples were examined with quantitative culture and immunofluorescent demonstration of ACB. From the results of quantitative culture, we divided specimens into pathogen-isolated and pathogen-free samples. Among pathogen-isolated samples, in which we isolated accepted pathogenic organisms at > or = 10(7) colony-forming units per ml, 16 of 23 samples were ACB-positive (69.5%). In contrast, among pathogen-free samples, in which we isolated accepted pathogens at < 10(7) colony forming units per ml or only upper respiratory flora, only 3 of 37 samples were ACB-positive (8.1%). The ACB-positive rate was significantly higher in pathogen-isolated than in pathogen-free samples (P < 0.001). Consequently, detecting ACB in expectorated sputum shows good potential as another criterion for distinguishing contaminating or colonizing organisms from true pathogens.

Diagnostic fiberoptic bronchoscopy in patients with community-acquired pneumonia. Comparison between bronchoalveolar lavage and telescoping plugged catheter cultures

We compared the diagnostic value of quantitative cultures of bronchoalveolar lavage (BAL) and telescoping plugged catheter (TPC) samples in 40 patients with moderately severe community-acquired pneumonia (CAP). None had received antibiotics previously. BAL quantitative cultures were performed in 13 control patients without pneumonia. In 28 (70 percent) patients, TPC cultures yielded > or = 10(3) cfu/ml of a pathogenic bacterium in pure culture. In 27 of these cases and in four additional cases, BAL cultures yielded > or = 10(3) cfu/ml. BAL cultures from the control group were sterile in seven cases, yielded normal flora in three cases, and yielded microorganisms thought to be not significant in two cases. Microbiologic agreement was reached by both TPC and BAL for 32 (84 percent) of 38 microorganisms recovered. Quantitative cultures from both techniques correlated very well (r = 0.71, p < 0.0001). We conclude that both TPC and BAL have similar accuracy to determine etiologic diagnosis of CAP. There was good qualitative and quantitative agreement between both techniques.

Pneumonia due to Haemophilus influenzae among mechanically ventilated patients. Incidence, outcome, and risk factors

Incidence and potential risk factors for pneumonia due to Haemophilus influenzae in adults treated with mechanical ventilation in a medical-surgical ICU were investigated. Diagnosis was established in 91 episodes and H influenzae was isolated in 20 of them. Mean onset of ventilator-associated pneumonia (VAP) due to H influenzae was 10.8 days after intubation. Six patients with H influenzae VAP died in the ICU. Of 13 risk factors for developing VAP due to H influenzae, an absence of prior antibiotic treatment was the only variable which had statistical significance (p < 0.001). In these mechanically ventilated patients, Haemophilus influenzae was a common causative agent for VAP, frequently associated with Gram-positive cocci. Episodes of H influenzae VAP were associated with a lower mortality compared with other etiologies. The epidemiologic and clinical findings indicate that patients without a prior antimicrobial treatment have increased susceptibility to infections of the airway by H influenzae.

Nosocomial respiratory tract infections in multiple trauma patients. Influence of level of consciousness with implications for therapy

A prospective study of 161 multiple trauma patients was carried out to determine the incidence, the causative agents, and the outcome of nosocomial respiratory tract infections in this highly selected population. Thirty-eight (23.6 percent) patients developed a nosocomial pneumonia (NP). In addition, there were four superinfections in three patients, representing an incidence of 26 percent (42 of 161). Incidence of NP was significantly greater among comatose patients (42.2 vs 13.3 percent, p less than 0.05). Furthermore, purulent tracheobronchitis was diagnosed in six patients. The causative agent of NP was identified in 36 (85.7 percent) episodes by means of fiberoptic bronchoscopies with protected specimen brush sampling. Staphylococcus aureus (55.8 percent) was the predominant pathogen isolated in multiple trauma patients in coma (Glasgow coma score [GCS] below 9 during a period greater than 24 h), while aerobic Gram-negative bacilli were responsible for the majority of cases in the remaining population studied. The overall mortality rate was 19.8 percent, but only five deaths were related to NP. We conclude that nosocomial respiratory tract infections are a frequent problem in multiple trauma patients, especially in those with GCS below 9, although this complication is associated with a relatively low mortality. Among patients with GCS below 9, S aureus was a frequent finding; consequently, antimicrobial therapy in this population needs to be different than that for the remaining multiple trauma patients with NP.

Pneumonia in the intensive care unit setting

Nosocomial pneumonia is a common and serious occurrence in the ICU. It most often results from aspiration of oropharyngeal secretions that have become colonized with pathogenic enteric gram-negative bacilli. Colonization occurs in association with acute and chronic illness and particularly with therapy that includes nasogastric or endotracheal tubes, H 2 blocking antacid drugs, or antibiotics; aspiration is increased by anesthesia, sedative drugs, and upper airway instrumentation. The diagnosis of ICU-acquired pneumonia is complicated greatly by the nonspecificity of clinical and laboratory data, and the difficulty in distinguishing the organisms producing infection from those merely colonizing the airway when using routine culture techniques. Among specialized diagnostic techniques, quantitative culture of specimens obtained with the protected sampling brush offers the most promise in establishing a specific microbacteriologic diagnosis of nosocomial pneumonia. Empirical treatment with broad spectrum antibiotics is frequently necessary when a specific diagnosis cannot be made. The poor outcome associated with nosocomial pneumonia, regardless of treatment, suggests that methods to prevent dissemination and oropharyngeal colonization of the offending organisms should be emphasized.

Chronic dyspnea unexplained by history, physical examination, chest roentgenogram, and spirometry. Analysis of a seven-year experience

The purpose of this article is to describe the spectrum and frequency of diseases presenting as unexplained dyspnea and to develop a logical diagnostic approach to such patients. Seventy-two consecutive physician-referred patients had dyspnea greater than one-month duration unexplained by the initial history, physical examination, chest roentgenogram, and spirometry. Patients underwent a standard diagnostic evaluation. A definite cause for dyspnea was recognized in 58 patients, and no answer was found in 14. Twenty-two diseases were recognized in the patient group. Dyspnea was due to pulmonary disease in 26 (36 percent) patients, cardiac disease in ten (14 percent) patients, hyperventilation in 14 (19 percent) patients, and only 3 patients had extrathoracic disease causing dyspnea. Age younger than 40 years, intermittent dyspnea, and normal alveolar-arterial oxygen pressure difference (P[A-a]O2) at rest breathing room air was strongly predictive of bronchial hyperreactivity or hyperventilation. No patient diagnosed as having disease of the lung parenchyma or vasculature had a P(A-a)O2 less than or equal to 20 mm Hg. The differential diagnosis to explain dyspnea in patients with nondirective histories, normal findings from physical examinations, normal chest roentgenograms, and normal spirograms is extensive. The patient's age and measurement of gas exchange at rest help to formulate a diagnostic approach.

Incidence, etiology, and outcome of nosocomial pneumonia in mechanically ventilated patients

This study assessed the incidence, etiology, and consequences of ventilator-associated pneumonia in 1,000 consecutive patients admitted in a medical-surgical intensive care unit (ICU). A total of 264 patients were submitted to mechanical ventilation (MV) for more than 48 hours. Fifty-eight (21.9 percent) patients developed a bacterial pneumonia after a mean of 7.9 days (range, 2 to 40 days) of MV. In addition, they were ten superinfections in nine patients, raising the mean incidence to 25.7 percent. Five patients developed secondary bacteremia, and another five had septic shock. Identification of the causative agent of pneumonia was possible in 47 episodes by means of highly specific techniques (telescoping plugged catheter, blood cultures, and/or necropsy). Thirteen (27.6 percent) of these cases were polymicrobial. The predominant pathogens isolated in the first episode of pneumonia were Gram-negative bacilli (62.6 percent), but a high incidence of Staphylococcus aureus infection (23.2 percent) was detected. Gram-negative bacilli represented 66.6 percent of the total organisms isolated in superinfections. The mortality rate in the pneumonia group was 42 percent; this percentage is similar to mortality rate among MV patients without pneumonia (37 percent). We conclude that nosocomial pneumonia is a frequent complication of MV in the medical-surgical ICU. Ventilator-associated pneumonia does not appear to increase fatality in critically ill patients with a high mortality rate (38 percent); however, it significantly prolongs the length of stay in the ICU for survivors.

Predictive value of oropharyngeal cultures for identifying lower airway bacteria in cystic fibrosis patients

Identifying lower respiratory pathogens in young, non expectorating cystic fibrosis (CF) patients has been problematic. Bronchial secretions are difficult to obtain, and little is known about lower airway flora in these patients. We collected simultaneous bronchial and oropharyngeal specimens in 43 CF patients in optimal respiratory status, including both expectorating (17) and nonexpectorating (26) patients, to determine the predictive value of oropharyngeal cultures for identifying lower airway pathogens. An additional goal was to characterize the lower respiratory flora of these patients. Predictive values were defined as the proportion of oropharyngeal culture results that accurately reflected the results of bronchial cultures. Predictive values of positive oropharyngeal cultures in nonexpectorating patients were 83% (95% confidence interval 36 to 100%) for Pseudomonas aeruginosa and 91% (59 to 100%) for Staphylococcus aureus. Predictive values of negative oropharyngeal cultures were lower: 70% (48 to 86%) for R aeruginosa and 80% (52 to 96%) for S. aureus. A relatively high proportion of nonexpectorating CF patients less than 10 yr old had R aerusginosa (11 of 24, 46%) or Klebsiella species (5 of 24, 21%) in their lower airways. The isolation of Klebsiella was associated with younger age (p = 0.03) and recent administration of antistaphylococcal antibiotics (p = 0.05). Our results suggest that oropharyngeal cultures yielding R aeruginosa or S. aureus are highly predictive, but such cultures lacking these organisms do not rule out the presence of these pathogens in the lower airways of CF patients.

The diagnostic utility of the antibody-coated bacteria test in intubated patients

PURPOSE

Pilot study to determine if the presence of antibody-coated bacteria (ACB) in sputum specimens obtained from endotracheal tube suctioning would aid in the diagnosis of lower respiratory tract infection (LRTI).

PATIENTS AND METHODS

All endotracheally intubated and mechanically ventilated patients for a two-month period were recruited for study. The diagnosis of LRTI was based on a clinical suspicion sufficient enough to start or change antibiotic therapy. Specimens were obtained by blind endotracheal tube suctioning. After processing, sputum smears were stained with fluorescein-labelled antibody to the Fc portion of IgG, IgM, and IgA. More than five fluorescein-labelled bacteria per oil immersion field were considered positive smears.

RESULTS

Seventy-one specimens were obtained from 36 patients. Eighteen specimens were positive in 12 patients, all of whom had LRTI. No specimen was positive in patients not diagnosed as having LRTI. The ACB test was positive in 12 of 25 patients with LRTI. Patients with LRTI but negative ACB were more likely to have received prior antibiotic therapy (p less than 0.001). ACB was positive prior to the clinical diagnosis of LRTI in seven of nine patients (av 4.1 days, range 2-6 days) and converted to negative in three specimens obtained seven or more days after starting appropriate antibiotics, while in three specimens it remained positive three-six days post treatment initiation.

CONCLUSIONS

The ACB test appears to be highly specific for the presence of LRTI in intubated patients. Sensitivity of the test may be adversely affected by prior antibiotic therapy. A positive ACB test may predict the subsequent development of LRTI. Further study is warranted.

Diagnostic fiberoptic bronchoscopy and protected brush culture in patients with community-acquired pneumonia

A model for performing fiberoptic bronchoscopy as a supplement to noninvasive diagnostic methods, in patients with community-acquired pneumonia, was prospectively studied. Twenty-four patients underwent bronchoscopy, seven pilot patients and 17 of 277 (6 percent) consecutive patients with CAP. Indications for FOB were early therapy failure (less than or equal to 72h)(n = 7), late therapy failure (greater than 72h)(n = 11), or before start of antibiotic therapy in severely ill or immunocompromised patients (n = 6). Samples were obtained by aspiration of bronchial secretion and with a protected brush catheter from which quantitative cultures with a detection level of 10(4) colony forming units per ml were performed. Results concluded that FOB, with the use of quantitative PB-cultures, offered a safe and specific diagnostic tool, which on special indications, can be of great value in the management of patients with CAP.

Quantification of nasopharyngeal bacteria for diagnosis of respiratory tract infection in children

Agreement between clinical signs of bacterial respiratory tract infections and quantities of respiratory tract pathogens in nasopharynx was studied in 77 children, aged 6-13 years. Specimens were obtained from 27 clinically bacterial and 51 clinically non-bacterial respiratory tract infections, and in 124 instances from healthy children. Viable counts of Streptococcus pneumoniae, Haemophilus influenzae, Branhamella catarrhalis, and beta-haemolytic streptococci were made from swab specimens suspended in saline before being plated on agar media. The frequency of these species in children with clinically bacterial, non-bacterial and no signs of respiratory tract infections were 85%, 47% and 26%, respectively. Bacterial counts greater than 10(4) colony-forming units (CFU)/ml of the pathogens occurred in 59% of clinically bacterial infections, as compared with 18% in clinically non-bacterial infections (p less than 0.001), the corresponding figures for counts greater than 10(3) CFU/ml being 85% and 41% (p less than 0.01), respectively. At neither level of bacterial count (i.e. greater than 10(4) or greater than 10(3], was there a significant difference between the healthy and those with a clinically non-bacterial infection. The quantification of bacteria in nasopharyngeal samples may thus be of clinical diagnostic value.

Comparison of tracheal aspirates and protected brush catheter specimens for identifying pathogenic bacteria in mechanically ventilated patients

Bacterial respiratory infections are common in patients undergoing prolonged mechanical ventilation, and antibiotic selection often is based upon the results of smears and cultures of tracheal aspirates (TA). This study was designed to determine the reliability of gram stains, cultures and antibody-coating of bacteria in TA by comparing them with the results of quantitative cultures of specimens obtained by protected brush catheters (PBC) inserted into involved areas of lung parenchyma. Twenty-two patients on mechanical ventilation for at least 72 hours, with new radiographic infiltrates and fever, were studied. Tracheal aspiration was performed in the usual manner using sterile disposable kits. Immediately thereafter, patients underwent fiberoptic bronchoscopy, and PBC-specimens were obtained from the areas of new radiographic infiltrates. Tracheal aspirates were gram stained and cultured aerobically, and antibody coating of bacteria was determined by fluorescence microscopy. Quantitative culture of PBC specimens contained greater than or equal to 10(3) colony forming units per brush in 16 of the 22 patients; a smaller number of organisms was present in two additional patients. In TA from all 22 patients, gram stains revealed polymorphonuclear neutrophils and bacteria. Cultures of TA revealed potential pathogens in 20 patients, and in 15, multiple pathogens were present. The bacteria isolated from PBC also were present in 14 of the 16 patients with greater than or equal to 10(3) CFU in PBC cultures (88%). Antibody coating was present in TA from 12 patients, and antibody coating correlated poorly with cultures of PBC specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchoscopic protected catheter brush for the diagnosis of pulmonary infections

A new bronchoscopic-protected catheter brush (BPCB), designed to obtain uncontaminated bronchial secretions, was studied in vitro and in vivo. The device was composed of a standard biopsy brush, protected by a single catheter and occluded with an agar plug. Ejection of the plug was obtained neither by advancing the brush nor by advancing an inner cannula (as in a telescoping catheter brush), but instead, by an air flux, provided by a syringe which was connected to the proximal tip. In the first part of the study the ability of the BPCB to obtain uncontaminated specimens was tested in comparison with the reference telescoping catheter brush (BFW brush 10/70/90, Medi-Tech Corp Watertown, MA). Catheters of each type were successively passed through the inner channel of a bronchofiberscope which was contaminated with Klebsiella pneumonia. After ejection of the distal plug, sampling of bronchial secretions infected with a marker organism (Pseudomonas aeruginosa), was performed with the brush. Culture of brush specimens of each type of catheter grew the marker organism in pure culture and obtained the same amount of bronchial secretions (0.001 ml). The manual vortexing of the brush in the transport medium (Ringer's solution) proved to be as effective as the mechanical vortexing so that transecting of the brush was no longer mandatory. In the second part of this study, paired bronchial samplings from 27 patients were performed using both types of catheters and similar results for both were obtained. In these in vitro studies, completed by a clinical trial, our single-sheathed, plugged catheter brush proved to be as reliable as the double telescoping catheter brush. However, because of its relatively simple conception, making it easier to use and lower in cost than the double catheter brush, routine use of this sampling device should be considered.

Rapid etiological diagnosis of pneumonia in young men

The major findings and conclusions of the present study are: 1. Evidence of the etiology of the pneumonia was established in 86% of 106 young men with pneumonia. Pneumococcus was the most common etiologic agent; it was detected definitely in 30% of the pneumonia patients, and possibly in another 20%, by blood culture, sputum culture, antigen detection, and serological methods. 2. Pneumococcal antigen detection from purulent pretreatment sputum samples was the best rapid diagnostic method for pneumococcus; it was capable of identifying 90% of the pneumococcal pneumonias definite by our criteria, whereas sputum Gram stain was positive in 65% of these. 3. Detection of adenoviral antigens from nasopharyngeal specimens (NPS) by EIA or IF method or adenovirus DNA by HYB method showed good specificity but a somewhat lower sensitivity than did adenovirus isolation from NPS. 4. Adenovirus antigens and DNA can be demonstrated also from sputum specimens. 5. EIA is slightly superior to the CF method in detecting antibody responses to adenovirus, but the detection of different antibody classes offers no additional diagnostic possibilities. 6. Isolation of Mycoplasma pneumoniae from bronchoalveolar fluid in pneumonia patients is a specific and sensitive method in the diagnosis of mycoplasmal pneumonia. 7. It seems possible to differentiate by clinical signs and symptoms and by high CRP (over 85mg/1) and WBC (over 10 x 10(9)/1) values pneumococcal pneumonias from viral, mycoplasmal and mixed pneumonias and from upper respiratory infections. Moderately elevated CRP values were observed in adenoviral (Mean 50 mg/1) and in mycoplasma (mean 59 mg/l) pneumonias, as well as in MRI (mean 44 mg/l).

Community-acquired pneumonia requiring hospitalization. Is it different in the elderly?

The authors studied 138 patients, 57 of whom were younger than 65 years of age and 81 who were 65 years of age and older, with community-acquired pneumonia to determine whether or not such pneumonia is different in the elderly and to define how such patients are investigated and treated. Pneumonia in the elderly was characterized by a higher mortality, 30 v 10%; more likely to be of unknown etiology, 54 v 30%; and more likely to show radiographic progression after the patient had been admitted to the hospital, 48 v 11%. In addition, elderly patients were more likely to be afebrile when admitted, 57 v 26%. Twenty-seven etiologic categories were present in 77 patients in whom a cause for the pneumonia was established. Streptococcus pneumoniae accounted for 9.4% of the pneumonia overall and for 27% of the pneumonia among patients who had sputum cultures performed before antibiotic therapy. The diagnostic yield was 11.6% for blood cultures, 38.2% for sputum cultures, 2.3% for throat washing, and 22.1% for serological studies. Twenty-seven percent of patients were receiving antibiotics of the time of admission to the hospital. Most (79%) received more than one antibiotic after admission. This study indicates that community-acquired pneumonia is a serious illness and that an algorithm approach to diagnosis and treatment of such pneumonia is necessary.

The use of fibreoptic bronchoscopy with sterile catheter in the diagnosis of pneumonia

The use of fibreoptic bronchoscopy with sterile catheter sampling of pulmonary secretions was evaluated in 70 patients with a provisional diagnosis of pneumonia. In 37 patients quantitative analysis of the sterile catheter isolates was performed (colony forming units (CFU) per ml). Potential bacterial pathogens were isolated in 37 patients and in the quantitative analysis, 14 of 22 isolates were grown in counts greater than or equal to 10(3) CFU/ml. Sterile catheter increased the bacterial isolation rate as in only 19 patients blood (2) or sputum (18) cultures yielded the same organisms. Sputum cultures showed a 25% false-positive rate in patients with no growth from sterile catheter. Quantitative analysis did not yield any further information in patients receiving antibiotics. Atypical or fungal pneumonia was diagnosed in 22 patients, while ten patients had other pathology simulating pneumonia. Sterile catheter sampling of pulmonary secretions at fibreoptic bronchoscopy proved to be a valuable tool in the diagnosis of bacterial pneumonia.